It's crunch time for Andy Murray who must beat Fernando Verdasco this afternoon to be sure of progressing to the semi-finals of the ATP World Tour Finals. Murray lost to world No 1 Roger Federer on Wednesday and must not slip up against the Spaniard if he is to prolong his time at the O2 Arena. Tom Bellwood has all the action.

6-7: MURRAY WINS THIRD SET AND MATCH! For the first time in the match, Murray showed real belief and dominated the tie-break. Verdasco goes out after losing all three of his round robin matches - Murray now has an anxious wait as the Federer v Del Potro will decide his fate.

6-6: So this match will be decided by a tie-break. Murray's future in thecompetition is still very much in doubt.

6-5: Verdasco says anything you can do, I can do better. Murray fails to return a single serve. Verdasco wins game.

5-5: Confusing all watching on, Murray shows real class to win this game in seconds. If he could control his serve as well as he did there, he would have made his life much easier in this match. Murray wins game.

4-5: A flying forehand volley from Verdasco leaves Murray rooted to the spot - it's level again and now just a matter of who is going to blink first to concede an inch. Verdasco wins game.

4-4: Whatever happens from here it seems unlikely Murray will be boosted by his performance today as he inches though his service games. Murray wins game.

3-4: Tremendous from Verdasco - he comes up with the answers when behind in games every time. Murray saw the door ajar to break but Verdasco cut him down with a powerful baseline volley. Verdasco wins game.

3-3: For all the talk of this being a roll-over for Murray now seems well off the mark. Verdasco is making Murray fight for every single point. Murray wins game.

2-3: Does anyone fancy another tie-break? Murray invests loads into an expansive rally but his forehand let him down. The set stays with serve. Verdasco wins game.

2-2: Murray's first-serve has gone a little awry and he is losing points regularly when he returns to Verdasco's backhand. Still, it's the first serves he does manage to squeeze in are too much for the Spaniard to handle. Murray wins game.

1-2: Murray trudges up and down the line showing some very negative body language - the cries from the crowd don't seem to help as yet another point goes to serve. Verdasco wins game

1-1: Another remarkably short game for Murray who cramps Verdasco up and wins in 57 seconds. Murray wins game

0-1: Verdasco's second serve has been great this afternoon and has really got him out of some tight spots but then his confidence gets the best of him as he double-faults to give Murray a break point.A Verdasco volley plants itself right on top of the net and just rolls over to win the point. More agony for Murray who is becoming vocal in his anger at how things are going. Verdasco wins game.

One of those days: Murray shows his displeasure as another point goes begging

0-0: Just as Verdasco gets his nose in front in game, Murray brings out the big guns and hammers to huge serves down the middle to win the game. Murray wins game.

7-6: Verdasco steals a point from Murray and another double-fault from the Scotsman wins the tie-break 7-4. VERDASCO WINS SECOND SET!

6-6: We're going into a tie- break at the end of the second set. Both players refuse to budge on their service games. Murray has the big powerful shots - Verdasco is playing some neat stuff around the net.

6-5: What a game! Verdasco recovers to win a 10-minute exchange that the Spaniard wins.

5-5: It's going right to the wire as the players trade wristy volleys to all corners of the court and the Spaniard is doing all he can to take this to a third set. Verdasco wins game

5-4: The crowd are warming to Verdasco who is showing real guts to not just roll over in this game.

4-4: Murray tries to find some tight angles but is unlucky to catch the top edge of the net with both. Verdasco wins game.

4-3: As clinical a game you will ever see. It lasted 53 seconds! Murray wins game.

Backs to the wall: Murray is struggling to close out in a match he has to win

3-3: Big point. Slow hand clapping from the 7,000 crowd as Verdasco calls for a review of a ball that looked well in - but it's out! The close-up of the official who called it right shows a beaming face.The Spaniard holds to serve-volley and win the game. Verdasco wins game.

3-2: Murray double faults to take his total for this match to six - John McEnroe accurately points out that he needs to cut that out if he wants to reach the very top of the sport. Murray wins game.

2-2: It's difficult to work Verdasco out as one moment he's playing beautifully expansive and powerful stokes and then he fluffs an easy looking forehand volley. Murray takes it to deuce but Verdasco closes it out with a big second serve that the Scot slices into the net. Verdasco wins game.

2-1: It's not time for Murray to be worrying yet but the Spaniard is certainly upping the aggression in this set - some great hustle wins a point that most would have given up on as lost and a fantastic stretching forehand volley down the line takes it deuce.But then some sloppy shot selection lets Murray back in. Murray wins game.

1-1: Verdasco shows no signs of pressure and wins a point with a deft volley at the net - he needed really soft hands to play that. Verdasco wins game.

Striking back: Verdasco hammers another forehand in the match with Murray

1-0: As straight-forward a game as Murray will ever win. Powerful serves earn two aces. Murray wins game.

0-0: Loose shots from Verdasco in straight-forward positions gives Murray the chance to break again but the Scot fails and smacks his racket into the ground in anger. A double-hand volley to baseline squeaks past Murray to take the first game. Verdasco wins game.

After a very nervy opening from both players, Murray finally takes his opportunity and breaks Verdasco - don't forget, if Murray wins in straight sets he'll definitely go through to the semi finals.

4-5: Murray serving for the set starts the game with a double fault and the crowd get a little anxious. Come on Tim - one thoroughly unfunny person squeals. Some more loose shots coming into the net take it to deuce - on four occasions as neither player closes out the game. But eventually Murray clubs a forehand and an error from Verdasco means ... MURRAY WINS FIRST SET.

Out in front: Murray celebrates taking a one set lead

4-4: Verdasco fails to take numerous opportunities to hammer volleys past Murray and then hits one return into the net - we have our first break of the match! Murray wins game.

4-3: Murray forces Verdasco further and further back and finishes with a deft touch over the net and then a double-hand cross court wins the game. Murray wins game

3-3: A great chance for Murray to break - he has one break point but a second-serve 111mph ace saves the Spaniard. That's his sixth ace in four games. Verdasco wins game.

3-2: A much, much better service game from Murray - deep and wide. Clinical. Murray wins game.

Murray's up: The Scotsman on his way to taking a nervy first set

2-2: Verdasco has been excellent with his first serve and is moving Murray across the width of the court as often as he can. The Spaniard definitely looks the more comfortable of the two out there in the early exchanges. Verdasco wins game.

1-2: Worrying signs for Murray who has signalled to his team that he is struggling to move. He then double faults and invites Verdasco on to increase the pressure. A smart back-hand volley wins the game. Murray wins game.

1-1: Murray wins the best point of the game - a flashing pass as Verdasco dipped near the net but it was the Spaniard who took the game to continue the tight opening to this match. Verdasco wins game.

0-1: Much more composure from Murray despite having a little trouble getting his first serve away. He slips as Verdasco forces him deep to take it to deuce but an ace and good accuracy with the subsequent serve wins the game. Murray wins game.

0-0: A fourteen point game to start this match as the two players exchange some powerful shots. The Spaniard had to fight back from the break points to take the first game. Verdasco wins game.

2.26: All the experts are calling this a straight-forward two-set victory for Murray which would be good as that would guarantee his place in the semis. Excellent. Verdasco to serve first.

Spanish ace: Verdasco attacks in the match with Murray

2.16: The two players huge ovations as they come strolling out to The Clash's London Calling - nice touch. Not quite the raucous atmosphere we experienced ahead of the Murray v Federer match but that's to be expected.

2.12: A quick chat with Darren Cahill reveals that Verdasco may suffer from a lack of confidence in these scenario's. His coach believes he has all the talent to push on but it's up to him to take his chances.

2.04: Some great insight from Greg Rusedski in the Sky studio - he's given Murray 10 out of 10 for his victory over Del Potro but 'less for the defeat to Federer.' Tar for that.

2pm: Afternoon all and welcome to Sportsmail's coverage of Andy Murray's final round-robin Group A match at the ATP World Tour Finals.

There was disappointment for Murray after his defeat to world No 1 Roger Federer in his last match on Wednesday night, going down 3-6 6-3 6-1 but victory against the Spaniard Verdasco this afternoon should be enough to get his challenge back on track.

But then he could still go through if Federer beats Juan Martin del Potro. Yep, it's complicated.

Still, Murray has plenty to prove today against the player who sent him crashing out of in the fourth round of the Australian Open earlier this year.

Aside from the defeat in Melbourne, Murray has beaten Verdasco in the seven other times the two players have met - so this should be a doddle!